3-Nitropyrazole compounds and anti-microbial compositions

ABSTRACT

New 3-nitropyrazole compounds of the formula: ##STR1## wherein R 1  is lower alkyl; 
     R 2  is hydrogen or lower alkyl; 
     R 3  is cyano, carboxyl or lower alkoxycarbonyl or the radical --CO--NR 4  R 5 , in which 
     R 4  is hydrogen or hydroxyl, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, thiocarbamoyl, ureido, thioureido, hydroxyphenyl, picolyl or is a lower alkyl, alkenyl or cycloalkyl radical substituted, if desired, by a cyano, hydroxyl, pyrrolidino, piperidino, amino, lower alkylamino, lower dialkylamino or lower acylamino substituent and 
     R 5  is a hydrogen atom or a lower alkyl radical or 
     R 4  and R 5  together represent a lower alkylene bridge; 
     And the pharmacologically compatible salts thereof, are outstandingly effective as anti-microbial agents, particularly systemically and in the urinary tract.

The present invention relates to novel 3-nitropyrazole compounds, toanti-microbial compositions containing them and to methods of combattingmicrobial infections utilizing such compounds.

The 3-nitropyrazole derivatives according to the present invention arecompounds of the general formula: ##STR2## wherein R₁ is lower alkyl;

R₂ is hydrogen or lower alkyl;

R₃ is cyano, carboxyl or lower alkoxycarbonyl or the radical --CO--NR₄R₅, in which

R₄ is hydrogen or hydroxyl, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl,thiocarbamoyl, ureido, thioureido, hydroxyphenyl, picolyl or is a loweralkyl, alkenyl or cycloalkyl radical substituted, if desired, by acyano, hydroxyl, pyrrolidino, piperidino, amino, lower alkylamino, lowerdialkylamino or lower acylamino substituent and

R₅ is a hydrogen atom or a lower alkyl radical or

R₄ and R₅ together represent a lower alkylene bridge; and thepharmacologically compatible salts thereof.

We have found that the new compounds according to the present inventionhave an outstanding anti-microbial action not only in vitro but also invivo and especially systemically and in the urinary tract.

The alkyl radicals in the definitions of the substituents R₁, R₂, R₄ andR₅, as well as the alkoxy radicals in the definition of the substituentR₃, can be straight-chained or branched and contain 1 to 5 andpreferably 1 to 3 carbon atoms. The methyl, ethyl and isopropyl radicalsare especially preferred as alkyl radicals and the methoxy radical isespecially preferred as the alkoxy radical.

When R₄ is an alkenyl radical, it can contain 2 to 5 and preferably 2 to3 carbon atoms, when R₄ is a cycloalkyl radical, it can contain 3 to 6carbon atoms and is preferably a cyclopropyl radical, when R₄ is anacylamino radical, it can contain 2 to 6 and preferably 2 to 4 carbonatoms, the acetylamino radical being especially preferred, and when R₄and R₅ together form an alkylene bridge, it can contain 4 or 5 butpreferably 5 carbon atoms.

The new compounds of general formula (I) according to the presentinvention can be prepared, for example, by one of the following methods:

a. reaction of a 3-nitro-4-formyl-pyrazole of the general formula:##STR3## wherein R₁ and R₂ have the same meanings as above, with acompound of the general formula:

    X--CH.sub.2 --R.sub.3                                      (III),

in which X is a hydrogen atom or R₃ and R₃ has the same meaning asabove, and, if X is R₃, the product is subsequently decarboxylated,possibly after previous saponification; or

b. reaction of a 3-aminopyrazole derivative of the general formula:##STR4## wherein R₁, R₂ and R₃ have the same meanings as above, underthe conditions of a nitro Sandmeyer reaction, to give the correspondingnitro compound, whereafter, if desired, in the compound thus obtained ofgeneral formula (I), a particular substituent R₃ is converted intoanother substituent R₃ by saponification, esterification,transesterification, amidation, transamidation, dehydration, alkylationor acylation.

The compounds of general formula (I) obtained by processes (a) and (b)can, if desired, be subsequently reacted with pharmacologicallycompatible acids or, when R₃ is a carboxyl radical, with non-toxicbases, to give the corresponding salts.

The reaction of 3-nitro-4-formyl-pyrazoles of the general formula (II)with compounds of the general formula (III) takes place according togenerally known methods, advantageously in an inert organic solvent, forexample pyridine, possibly in the presence of a little piperidine, andat an elevated temperature. When X in general formula (III) represents ahydrogen atom, there can also be used reactive derivatives of compoundsof general formula (III), for example a carboxylic acid anhydride.

3-Amino-pyrazole derivatives of general formula (IV) are converted intothe nitro compounds of general formula (I) in the usual manner,preferably by reaction with an alkali metal nitrite, for example sodiumor potassium nitrite, and a mineral acid in the presence of copperpowder as catalyst at a temperature of from -10° to +30° C., via thecorresponding diazonium salt.

The subsequent conversion of a substituent R₃ into a differentsubstituent R₃ can be carried out in the usual manner by saponification,esterification, transesterification, amidation, transamidation,dehydration, alkylation or acylation.

Thus, for example, a compound in which R₃ is a cyano group can besubsequently saponified in the usual manner to give the correspondingcarboxylic acid of general formula (I) in which R₃ is a carboxylradical. This reaction is preferably carried out with a strong acid, forexample, concentrated hydrochloric acid, or with an aqueous solution ofan alkali metal hydroxide, for example a 20% aqueous solution of sodiumhydroxide. By the choice of suitable reaction conditions, it is possibleto hydrolyse the nitrile group to the carboxylic acid amide stage, forexample, with 98% sulphuric acid or with an aqueous, alkaline solutionof hydrogen peroxide.

On the other hand, if desired, a carboxylic acid amide of the generalformula (I) can be subsequently converted in known manner into thecorresponding nitrile (R₃ in general formula (I) = CN), for example, bytreatment with phosphorus oxychloride at an elevated temperature.Furthermore, it is possible to convert a carboxylic acid ester ofgeneral formula (I) (R₃ = alkoxycarbonyl) into the correspondingcarboxylic acid (R₃ = carboxyl), by saponification. This saponificationis carried out in the usual way, preferably by treatment of thecarboxylic acid ester with a dilute aqueous solution of an alkali metalhydroxide at an elevated temperature.

On the other hand, a carboxylic acid of general formula (I) (R₃ =carboxyl) can be esterified in the usual manner to give thecorresponding alkoxycarbonyl compound, for example by reaction with alower alcohol and preferably with methanol or ethanol, in the presenceof a hydrogen halide.

The conversion of a carboxyl group into an ester function can also takeplace in two stages by first converting the carboxylic acid in the usualmanner into a reactive carboxylic acid derivative, for example, into acarboxylic acid chloride, and subsequently reacting this with a loweralcohol, preferably with methanol or ethanol, or with a correspondingalkali metal alcoholate, preferably a sodium or potassium alcoholate, togive the desired carboxylic acid ester of general formula (I).

Furthermore, it is possible to convert an alkoxycarbonyl compound ofgeneral formula (I) into an alkoxycarbonyl compound of general formula(I) with a different alkoxy radical by reaction with an appropriatelower alcohol, in known manner, preferably in the presence of an acid orbase as catalyst.

The conversion of a compound of general formula (I), in which R₃ is acarboxyl group, into a corresponding carboxylic acid amide of generalformula (I) (R₃ = --CO--NR₄ R₅) which it may possibly be desired tocarry out, is generally carried out in known manner, for example, byreaction of a carboxylic acid or of a carboxylic acid ester of generalformula (I) with ammonia or a substitution product thereof. However,here, too, it is especially preferred first to convert the carboxylicacid in known manner into a reactive derivative, for example into acarboxylic acid chloride, and then to react this with ammonia or with asubstituted derivative thereof to give the desired carboxylic acidamides of general formula (I). This last reaction step can be carriedout in the usual manner, preferably in the presence of an inert organicsolvent, for example, pyridine, dioxan or toluene, possibly in admixturewith water, and, depending upon the reactivity of the reactioncomponents, at a temperature of from -20° to +200° C.

One form of subsequent N-alkylation is the reaction of a primary orsecondary amide of general formula (I) by the Mannich reaction with asecondary amine, for example, pyrrolidine, piperidine or dialkylamines,in the presence of formaldehyde and usually in an aqueous organic phase,at an elevated temperature, N',N'-disubstituted N-aminomethyl-carboxylicacid amides of general formula (I) thereby being formed.

When an amino group is present in the substituent R₄, it can, ifdesired, be subsequently acylated in known manner with a conventionalacylation agent, for example, a carboxylic acid chloride or carboxylicacid anhydride.

Furthermore, it is possible to convert a carboxylic acid amide ofgeneral formula (I) (R₃ = --CO--NR₄ R₅ ; R₄ = R₅ = H), via thecorresponding carbonyl isocyanate, into an N-carbamoyl-carboxylic acidamide of general formula (I) (R₃ = --CO--NR₄ R₅ ; R₄ = carbamoyl,alkylcarbamoyl or dialkylcarbamoyl; R₅ = H). The conversion of acarboxylic acid amide into a carbonyl isocyanate is carried out in theusual manner, preferably by reaction of the carboxylic acid amide withoxyalyl chloride in an inert organic solvent, for example chlorobenzene,at an elevated temperature. By the addition of ammonia or of analkylamine or dialkylamine to the carbonyl isocyanate obtained, there isformed, in known manner, the desired carboxylic acid ureide derivativeof general formula (I).

The starting compounds of general formula (II) can be obtained byconverting 3-amino-4-alkoxycarbonylpyrazole derivatives (cf. Helv. Chim.Acta, 42, 349/1959) into the corresponding 3-nitro compounds, forexample with an alkali metal nitrite and a mineral acid in the presenceof copper powder, the carboxylic acid ester function being saponified,if desired, in known manner to give the free carboxylic acid group. The3-nitro-4-carboxyl-pyrazole or 3-nitro-4-alkoxycarbonyl-pyrazolederivatives obtained can then be converted by known methods into thealdehyde compounds of general formula (II).

Thus, for example, it is possible to convert an appropriatelysubstituted 3-nitropyrazole-4-carboxylic acid into the correspondingcarboxylic acid chloride, to reduce this, for example, with lithiumaluminium tri-tert.-butoxy hydride, at a low temperature to give amixture of a 3-nitropyrazole-4-aldehyde and of a3-nitro-4-hydroxymethyl-pyrazole derivative and to treat this mixturewith an appropriate oxidation agent, preferably lead tetraacetate, inorder also to convert its hydroxymethyl component into the desiredaldehyde of general formula (II). The free 3-nitropyrazole-4-carboxylicacid or a corresponding ester can also be completely reduced to a3-nitro-4-hydroxymethylpyrazole derivative, for example with sodiumborohydride, with or without anhydrous aluminium chloride, andsubsequently oxidised with, for example, lead tetraacetate, to give a3-nitropyrazole-4-aldehyde compound of general formula (II).

The starting compounds of general formula (IV) can be prepared byconverting a 3-amino-4-alkoxycarbonylpyrazole derivative (cf. Hlv. Chim.Acta, 42, 349/1959) to the corresponding 3-aminopyrazole-4-aldehydederivative. In principle, this can take place in the same manner asdescribed above for the analogous 3-nitro compounds. The3-aminopyrazole-4-aldehyde derivatives obtained can then be reacted inknown manner with malonic acid or with a derivative thereof in a manneranalogous to process variant a) to give the desired3-aminopryazole-4-acrylic acid derivatives of general formula (IV).

For the conversion of compounds of general formula (I) intopharmacologically compatible salts, the compounds are reacted in theusual manner, preferably in an organic solvent, with an equivalentamount of a non-toxic inorganic or organic acid, for example,hydrochloric acid, hydrobromic acid, phosphoric acid, sulphuric acid,acetic acid, citric acid, lactic acid, malic acid, salicyclic acid,malonic acid, maleic acid, succinic acid or benzoic acid or, when R₃ isa carboxyl radical, with an equivalent amount of a non-toxic inorganicor organic base.

For the preparation of pharmaceutical compositions, the compounds (I)are mixed in the usual manner with appropriate pharmaceutical carriermaterials, aroma, flavoring or coloring materials and formed, forexample, into tablets or dragrees or, with the addition of appropriateajuvants, suspended or dissolved in water or in an oil, for example,olive oil.

The compounds of general formula (I) according to the present inventionand the salts thereof can be administered enterally or parenterally inliquid or solid form. As injection medium, it is preferable to use waterwhich contains the additives usual in the case of injection solutions,such as stabilising agents, solubilising agents or buffers. Additives ofthis type include, for example, tartrate and citrate buffers, ethanol,complex-forming agents (such as ethylenediamine-tetraacetic acid and thenon-toxic salts thereof) and high molecular weight polymers (such asliquid polyethylene oxide) for viscosity regulation. Solid carriermaterials include, for example, starch, lactose, mannitol, methylcellulose, talc, highly-dispersed silicic acid, high molecular weightfatty acids (such as stearic acid), gelatine, agar-agar, calciumphosphate, magnesium stearate, animal and vegetable fats and solid highmolecular weight polymers (such as polyethylene glycols). Compositionssuitable for oral administration can, if desired, contain flavoring andsweetening materials.

Apart from the compounds specifically mentioned in the followingExamples, the following compounds are also preferred according to thepresent invention:

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-isopropylamide; m.p.189°-192° C.;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-cyanomethylamide; m.p.172°-174° C.;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-acetylaminoethylamide;m.p. 246°-249° C.;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid thioureide; m.p. 211°-212°C.

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid semicarbazide;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-piperidinomethylamide;m.p. 185°-186° C.;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-aminoethylamide;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(N'-methylcarbamoyl)-amide; m.p. 257°-258° C.;

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N',N'-dimethylureide; m.p.174°-176° C.; and

3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-methyl-N-aminoethylamide.

The following Examples are given for the purpose of illustrating thepresent invention:-

EXAMPLE 1 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acid

6.3 g. 1-methyl-3-nitropyrazole-4-aldehyde are stirred with 4.45 g.malonic acid and 2 ml. pyridine for 30 minutes at 100° C. The reactionmixture is cooled and the mass obtained is triturated with isopropanol,filtered off with suction and washed with isopropanol and diethyl ether.The crystals obtained are then triturated with water and thereafterfiltered off with suction and dried at 80° C. in a vacuum. There areobtained 4.86 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid; m.p.222°-223° C.

In an analogous manner from 1,5-dimethyl-3-nitropyrazole-4-aldehydethere is obtained 3-(1,5-dimethyl-3-nitro-4-pyrazolyl)-acrylic acid;m.p. 192°-194° C.

The 1-methyl-3-nitropyrazole-4-aldehyde used as starting material isprepared in the following manner:

a. 1-Methyl-3-nitropyrazole-4-carboxylic acid

1.55 g. 1-methyl-3-amino-4-carbomethoxypyrazole (see Helv. Chim. Acta,42, 349/1959) are dissolved in 8.8 ml. 35% hydrofluoboric acid and 10ml. water. This solution is poured into a solution, with a temperatureof 5° C., which contains 10 g sodium nitrite in 50 ml. water, as well as1 g. copper powder. The reaction mixture is stirred for 2 hours atambient temperature and filtered and the residue is washed with ethylacetate. The combined filtrates are extracted with ethyl acetate and theextract is dried and evaporated. The residue (1.65 g.) is stirred for 30minutes in 16.5 ml. 2N aqueous sodium hydroxide solution at 100° C. Thereaction mixture is then cooled and filtered and the filtrate isacidified with 6N hydrochloric acid. After filtering off the precipitatewith suction, washing with water and drying, there is obtained 0.7 g.1-methyl-3-nitropyrazole-4-carboxylic acid; m.p. 186°-188° C.

b. 1-Methyl-3-nitropyrazole-4-aldehyde Variant I

15 g. 1-methyl-3-nitropyrazole-4-carboxylic acid are boiled under refluxfor 1 hour with 150 ml. thionyl chloride. The solution obtained isevaporated in a vacuum and the residue obtained is triturated with 60ml. petroleum ether to give 16 g. 1-methyl-3-nitropyrazole-4-carboxylicacid chloride; m.p. 68°-70° C.

14.6 g. of this acid chloride are dissolved in 155 ml.1,2-dimethoxyethane, 20 g. lithium aluminium tritert.-butoxy hydride areintroduced portionwise at -60° to -70° C. in the course of 45 minutesand the reaction mixture is then stirred for 1 hour, the temperaturethereby being allowed to increase slowly to 0° C., whereafter thereaction mixture is poured into 0.5 liters of ice-water. The precipitateobtained is filtered off with suction and the clear filtrate issaturated with sodium chloride and extracted three times with ethylacetate. The combined extracts are washed with an aqueous solution ofsodium bicarbonate, dried in a vacuum and evaporated. There are obtained5 g. of evaporation residue which, according to the thin layerchromatogram, consists of about equal parts of1-methyl-3-nitropyrazole-4-aldehyde and1-methyl-3-nitro-4-hydroxymethyl-pyrazole.

This mixture is dissolved in 250 ml. hot toluene, 25 g. leadtetraacetate are added thereto portionwise, while stirring, and thereaction mixture is subsequently boiled under reflux for 1 hour. Afurther 5 g. lead tetraacetate are then added and the reaction mixtureis further boiled under reflux for 1 hour, cooled and the lead salt thenfiltered off with suction. The toluene filtrate is shaken up with asaturated aqueous solution of sodium carbonate, undissolved material isfiltered off with suction and the organic phase in the filtrate isseparated off. After drying and evaporating the toluene solution, thereare obtained 4.85 g. 1-methyl-3-nitropyrazole-4-aldehyde which,according to the thin layer chromatogram, is practically uniform.

Variant II

0.52 g. 1-methyl-3-nitropyrazole-4-carboxylic acid is introducedportionwise, while stirring, into a solution of 0.11 g. sodiumborohydride in 3 ml. anhydrous diethylene glycol dimethyl ether, thetemperature thereby increasing to about 45° C. A solution of 0.13 g.anhydrous aluminium chloride in 5 ml. anhydrous diethylene glycoldimethyl ether is now added slowly thereto, the reaction mixture isstirred for 1 hour at ambient temperature and for 1 hour at 60°-65° C.,a further 0.05 g. sodium borohydride and 0.06 g. anhydrous aluminiumtrichloride are added thereto and the reaction mixture again stirred for1 hour at 60°-65° C.

The reaction mixture is now cooled, poured on to crushed ice, to whichsome concentrated hydrochloric acid has been added, and extracted threetimes with ethyl acetate. The combined extracts are dried, evaporated ina vacuum at a bath temperature of 70° C. and the evaporation residue istriturated with petroleum ether. There is thus obtained 0.45 g. crude1-methyl-3-nitro-4-hydroxymethylpyrazole which, after treatment with alittle aqueous sodium bicarbonate solution, filtering with suction andwashing with water, melts at 150°-152° C.

Alternatively, 12 g. 1-methyl-3-nitropyrazole-4-carboxylic acid in 300ml. ethanol saturated with gaseous hydrogen chloride can be left tostand for 12 hours at ambient temperature and the reaction mixture thenworked up to give 13.3 g. ethyl 1-methyl-3-nitropyrazole-4-carboxylate;m.p. 69°-71° C.

7.62 g. of this ester are added, with stirring, to a suspension of 1.35g. sodium borohydride in 63 ml. 1,2-dimethoxyethane. To this is addedportionwise, while stirring, 1.6 g. aluminium chloride, the temperaturenot being allowed to rise above 50° C., followed by stirring for 2 hoursat 65° C. After a further addition of 0.34 g. sodium borohydride and 0.4g. aluminium chloride and further stirring for 1.5 hours at 65° C., thesuspension is evaporated in a vacuum at a bath temperature of 50° C. Theevaporation residue is suspended in about 50 ml. water, the pH isadjusted to about 1 with concentrated hydrochloric acid, filtered withsuction, washed with water and dried to give 4.96 g.1-methyl-3-nitro-4-hydroxymethyl-pyrazole; m.p. 150°-153° C.

1.57 g. of the 1-methyl-3-nitro-4-hydroxymethyl-pyrazole thus obtainedin 75 ml. hot toluene is mixed, while stirring, with 6.65 g. leadtetraacetate, followed by stirring for 1.5 to 2 hours under reflux.After cooling, the lead salt is filtered off with suction, the filtrateis shaken up with 2N aqueous sodium carbonate solution and the organicphase is separated off, dried and evaporated in a vacuum to give 1.46 g.1-methyl-3-nitropyrazole-4-aldehyde. After trituration with a littleisopropanol and washing with isopropanol and diethyl ether, the meltingpoint is 81°-83° C. The yield of purified product is then 0.85 g.

EXAMPLE 2 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acid ureide

2 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid (preparation seeExample 1) are stirred under reflux for 1 hour with 24 ml. oxalylchloride, whereafter the solution is evaporated in a vacuum. Somepetroleum ether is added to the evaporation residue, followed byevaporating again and this latter process is repeated once more in ordercompletely to remove oxalyl chloride and hydrochloric acid. There arethus obtained 2.19 g. crude 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid chloride; m.p. 84°-86° C.

To a suspension of 0.46 g. urea in 14 ml. pure pyridine, there is addeddropwise, within the course of 15 minutes, while stirring at 50° C., asolution of 1.5 g. of this crude3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride in 14 ml. drydioxan, followed by stirring for 2 hours at 50° C. The reaction mixtureis then cooled to ambient temperature, filtered with suction to removeundissolved material, washed with dioxan and diethyl ether and theproduct thus obtained (1.5 g.) triturated with 3 ml. water. It is nowfiltered off with suction, washed with water and diethyl ether and driedto give 0.95 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid ureide;m.p. 244°-246° C. (with foaming).

EXAMPLE 3 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylamide

From 1.26 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid (preparationsee Example 1) and 15 ml. oxalyl chloride, there is prepared, in themanner described in Example 2, the corresponding acrylic acid chlorideand this is dissolved in 45 ml. pure toluene. Dry ammonia gas is passedinto this solution for 15 minutes at 15°-20° C., while stirring. Theprecipitated crystals are filtered off with suction, washed with tolueneand, after drying, triturated with water. The product is again filteredoff with suction, washed with water and ethanol and dried in a vacuum at110° C. There is thus obtained 1.17 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylamide; m.p. 255°-257° C. (changeabove 248° C.). The product still contains about 1/3 mol water.

In an analogous manner, from3-(1,5-dimethyl-3-nitro-4-pyrazolyl)-acrylic acid, there is obtained,via its acid chloride and ammonia gas,3-(1,5-dimethyl-3-nitro-4-pyrazolyl)-acrylamide; m.p. 225°-229° C.

EXAMPLE 4 3-(1-Methyl-3-nitro-4-pyrazolyl)-N-hydroxyacrylamide

8.12 g. hydroxylamine hydrochloride are dissolved in 100 ml. methanol,and 9.35 g. sodium hydroxide in 140 ml. methanol added thereto. Theprecipitated sodium chloride is separated off and the solution is madeup to 250 ml. with methanol. 12.5 ml. of this solution (containing 0.193g. hydroxylamine) are mixed portionwise at 0° C. with 0.54 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride (preparation seeExample 2) and thoroughly stirred for 15 minutes at 0° C. Thetemperature is then allowed to increase to ambient temperature and solidmaterial is filtered off with suction and washed with methanol. Theyellow-brown substance thus obtained is suspended in about 3 ml. waterand well acidified with 2N hydrochloric acid. The beige-colouredsubstance obtained is filtered off with suction, washed with water anddried in a vacuum. There is thus obtained 0.36 g.3-(1-methyl-3-nitro-4-pyrazolyl)-N-hydroxyacrylamide; m.p. 172°-174° C.(with foaming). 0.1 g. of this substance is recrystallised from 2 ml. ofa dioxan-water mixture (9:1), with the addition of active charcoal. Therecrystallised product has a melting point of 183°-184° C.

EXAMPLE 5 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(β-hydroxyethyl)-amide

Into a solution of 0.6 g. β-hydroxyethylamine in 12 ml. methanol, thereis introduced portionwise at 0° C., 0.65 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride (preparation seeExample 2). The reaction mixture is stirred for 10 minutes at 0° C. andthereafter for 30 minutes at ambient temperature. The solid material isthen filtered off with suction and washed with methanol and diethylether to give 0.42 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(β-hydroxyethyl)-amide; m.p. 176°-178° C. (with foaming).

EXAMPLE 6 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acidthiosemicarbazide

To a suspension of 0.3 g. thiosemicarbazide in 6 ml. anhydrous pyridineis added dropwise at 2°-3° C., in the course of 45 minutes, a solutionof 0.65 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride(preparation see Example 2) in 6 ml. dioxan. The reaction mixture isstirred for 1 hour at 2°-3° C. and for 1 hour at ambient temperature.The suspension is then evaporated in a vacuum and the solid residuetriturated with 1N hydrochloric acid. After filtering with suction andwashing with water, there is obtained 0.68 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid thiosemicarbazide; m.p.208°-210° C. (with foaming).

EXAMPLE 7 3-(1-Ethyl-3-nitro-4-pyrazolyl)-acrylic acid

20 g. 3-nitro-4-pyrazole-carbonitrile are stirred with 17.5 ml. ethyliodide, 21 g. potassium carbonate and 145 ml. 1,2-dimethoxyethane for 2hours under reflux, followed by cooling. The inorganic material is thenfiltered off with suction. The filtrate is evaporated in a vacuum, theevaporation residue is dissolved in about 250 ml. ethyl acetate and thissolution is shaken up with 150 ml. aqueous 2N potassium carbonatesolution and with sodium thiosulphate solution. The organic phase isseparated off, dried and evaporated in a vacuum to give 21.7 g. crude1-ethyl-3-nitro-4-pyrazole carbonitrile in the form of an oil.

15.7 g. 1-ethyl-3-nitro-4-pyrazole carbonitrile are introduced into asolution of 15.7 g. solid sodium hydroxide in 170 ml. water and stirredunder reflux for 1 hour, the oil thereby slowly going into solution.After cooling, it is well acidified with concentrated hydrochloric acidand the precipitated crystals are filtered off with suction, washed withwater and dried. There are thus obtained 12.45 g. crude1-ethyl-3-nitropyrazole-4-carboxylic acid; m.p. 160°-163° C. (changefrom 155° C.).

9.25 g. of this acid are stirred for 1 hour under reflux with 90 ml.thionyl chloride. The solution is then evaporated in a vacuum, petroleumether is added thereto and the mixture again evaporated. The oilyevaporation residue (crude 1-ethyl-3-nitropyrazole-4-carboxylic acidchoride) is now dissolved in 30 ml. anhydrous 1,2-dimethoxyethane and,while stirring at -60° to -70° C., a solution of 12.8 g. lithiumaluminium tri-tert.-butoxy hydride in 50 ml. anhydrous dimethoxyethaneis added dropwise over the course of 45 minutes. The reaction mixture isthereafter stirred for 1 hour, the temperature being allowed to increaseslowly to 0° C. 250 ml. ice water are now poured in, the precipitate isfiltered off with suction and the aqueous filtrate is saturated withsodium chloride and extracted three times with ethyl acetate. Thecombined extracts are shaken with 2N aqueous sodium carbonate solution,the ethyl acetate phase is separated off and, after drying, evaporatedin a vacuum, 3.15 g. of an oily residue remaining behind. According tothe thin layer chromatogram, there is present a mixture of about equalparts of 1-ethyl-3-nitro-4-hydroxymethylpyrazole and1-ethyl-3-nitropyrazole-4-aldehyde, which is further worked up withoutfurther purification.

This 3.15 g. of oily mixture are well mixed with 2.03 g. malonic acidand 0.95 ml. pyridine and heated to a bath temperature of 100° C., avigorous evolution of gas thereby taking place. The reaction mass iskept for 30 minutes at 100° C., then cooled and triturated three timeswith diethyl ether and then with about 7 ml. of a water-isopropanolmixture (7:3). The crystals obtained are filtered off with suction andwashed with a little isopropanol and diethyl ether. There is thusobtained 0.82 g. crude 3-(1-ethyl-3-nitro-4-pyrazolyl)-acrylic acid;m.p. 219°-220° C. (change above 191° C.).

EXAMPLE 8 3-(1-Ethyl-3-nitro-4-pyrazolyl)-acrylamide

0.82 g. 3-(1-ethyl-3-nitro-4-pyrazolyl)-acrylic acid is stirred with 10ml. oxalyl chloride for 1 hour under reflux. The solution is thenevaporated in a vacuum and petroleum ether is added thereto, followed byevaporating again. The latter procedure is preferably repeated in orderto remove oxalyl chloride and hydrochloric acid as completely aspossible. The oily evaporation residue is crude3-(1-ethyl-3-nitro-4-pyrazolyl)-acrylic acid chloride. This is dissolvedin 30 ml. anhydrous toluene and, while stirring, ammonia gas is passedin for 15 minutes at 15°-20° C. The product which thereby precipitatesout is filtered off with suction, washed with toluene and dried. Thecrystals thus obtained are thoroughly triturated with water, filteredoff with suction, washed with water and ethanol and finally dried in avacuum at 100° C. There is thus obtained 0.75 g.3-(1-ethyl-3-nitro-4-pyrazolyl)-acrylamide; m.p. 210°-212° C. (changeabove 203° C.).

EXAMPLE 9 Methyl 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylate

1.3 g. of the 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid described inExample 1 is dissolved in 52 ml. warm methanol and the solutionsaturated at ambient temperature with gaseous hydrogen chloride andthereafter left to stand overnight. The reaction solution is thenevaporated in a vacuum at ambient temperature (bath temperature) and theevaporation residue is triturated with a saturated aqueous solution ofsodium bicarbonate, filtered off with suction and washed with water togive 1 g. methyl 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylate; m.p.110°-112° C.

The same product is obtained when 0.22 g. of the3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride described inExample 2 is allowed to react in 1.8 ml. methanol for 30 minutes atambient temperature and the resultant crystals filtered off withsuction.

EXAMPLE 10 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(6-methyl-2-pyridyl)-amide

0.215 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride(preparation see Example 2) is dissolved in 3 ml. dioxan and mixed atambient temperature, while stirring, with 2-amino-6-methylpyridine.After a short time, crystals begin to precipitate out. Stirring iscontinued for 30 minutes at ambient temperature, followed by dilutionwith water. The solid is filtered off with suction and then washed withwater. After drying, there is obtained 0.23 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(6-methyl-2-pyridyl)-amide; m.p. 191°-193° C.

EXAMPLE 11 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acid N-methylamide

0.54 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride(preparation see Example 2) is dissolved in 20 ml. anhydrous tolueneand, while stirring at 25° C., methylamine gas is passed in for about 10minutes. The precipitated crystals are filtered off with suction, washedwith toluene, triturated with water and dried in a vacuum. There is thusobtained 0.43 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-methylamide; m.p. 200°-203° C.

EXAMPLE 12 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(4-hydroxyphenyl)-amide

0.43 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride(preparation see Example 2) is dissolved in 6 ml. dioxan and 0.64 g.4-hydroxyaniline is added thereto, while stirring, stirring beingcontinued for 30 minutes at ambient temperature. The precipitatedcrystals are filtered off with suction and washed with dioxan and thenwith water. After drying in a vacuum at 100° C., there is obtained 0.58g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(4-hydroxyphenyl)-amide; m.p. 290°-293° C. (with foaming).

EXAMPLE 13 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(pyrrolidinomethyl)-amide

1 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylamide (preparation seeExample 3) is mixed with 3.5 ml. methanol, 1 ml. pyrrolidine and 0.9 ml.37% aqueous formaldehyde solution and stirred under reflux for 4 hours.A further 1 ml. pyrrolidine and 0.9 ml. formaldehyde solution are addedthereto and the reaction mixture is kept under reflux for a further 3hours. 1 ml. pyrrolidine and 0.9 ml. formaldehyde are again addedthereto and stirring under reflux continued for a further 6 hours. Thereaction mixture is then completely evaporated to dryness in a vacuum,the residue is triturated with methanol and the solid material isfiltered off with suction. There is thus obtained 0.34 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acidN-(pyrrolidinomethyl)-amide; m.p. 180°-183° C. It is soluble in dilutehydrochloric acid. A further 0.35 g. of the same compound is obtainedfrom the mother liquor by evaporation.

EXAMPLE 14 3-(1 -Methyl-3-nitro-4-pyrazolyl)-acrylic acid N-allylamide

1.1 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride(preparation see Example 2) is dissolved in 15 ml. pure dioxan and 1.14ml. allylamine added thereto, while stirring, the temperature therebyincreasing to about 45° C. and an oil separates out. The reactionmixture is evaporated in a vacuum, the residue is triturated with waterand the crystals obtained are filtered off with suction. After washingwith water and drying in a vacuum at 100° C., there is obtained 0.94 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-allylamide; m.p.143°-146° C.

EXAMPLE 15 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylic acidN-cyclopropylamide

0.645 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid chloride(preparation see Example 2) is dissolved in 6 ml. anhydrous dioxan and0.513 g. cyclopropylamine added thereto, while stirring and cooling. Thereaction mixture is further stirred for 30 minutes at ambienttemperature and the precipitated substance (0.72 g.) is filtered offwith suction and triturated with water to give 0.6 g.3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid N-cyclopropylamide; m.p.183°-185° C. (with foaming) in the form of bright yellow crystals.

In an analogous manner, from 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid chloride, there is obtained by reaction with

a. piperidine, 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid piperidine;m.p. 190°-191° C.;

b. N,N-diethylethylenediamine, 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid N-diethylaminoethylamide; m.p. 109°-110° C.

EXAMPLE 16 Methyl 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylate

0.5 g. 1-methyl-3-nitro-pyrazole-4-aldehyde and 0.85 g. monomethylmalonate are stirred in 1.6 ml. pyridine and 0.04 ml. piperidine for 2hours at 100° C. The reaction mixture is then cooled, poured on to iceand acidified with dilute hydrochloric acid. The suspension is filteredoff with suction and washed with water until neutral. After drying,there is obtained 0.45 g. (66% of theory) of the desired methyl3-(1-methyl-3-nitro-4-pyrazolyl)-acrylate; m.p. 110°-112° C. The mixedmelting point with the product obtained in Example 9 shows nodepression.

EXAMPLE 17 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylamide

0.5 g. 1-methyl-3-nitropyrazole-4-aldehyde and 0.65 g. malonic acidmonoamide are dissolved in 1.6 ml. pyridine, mixed with 1 drop ofpiperidine and stirred for 1.75 hours at 100° C. The reaction mixture isthen cooled and poured on to ice and the suspension is filtered off withsuction. It is thoroughly washed with water and dried to give 0.25 g.(40% of theory) of the desired3-(1-methyl-3-nitro-4-pyrazolyl)-acrylamide.

When the reaction of 1-methyl-3-nitropyrazole-4-aldehyde and malonicacid monoamide in pyridine is carried out at 70° C., then, asintermediate product, there can be isolated2-carbamoyl-3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid. Fordecarboxylation, 0.1 g. of this product is stirred in 1 ml. pyridine for1.5 hours at a bath temperature of 120° C. The reaction mixture is thencooled, ice-cold semi-concentrated hydrochloric acid is added theretoand the precipitated crystals are filtered off with suction, washed withwater and dried. There is obtained 0.02 g.3-(1-methyl-3-nitropyrazolyl)-acrylamide.

The mixed melting point with the product obtained in Example 3 shows nodepression.

The 1-methyl-3-nitropyrazole-4-aldehyde used as starting material isobtained as follows:

0.97 g. 3-(5)-amino-4-methylpyrazole (see Chem. Abs., 59, 5147/1963) isdissolved in 8.8 ml. 35% hydrofluoboric acid and 10 ml. water. Thissolution is poured into a solution, with a temperature of 5° C., whichcontains 10 g. sodium nitrite in 50 ml. water, as well as 1 g. copperpowder. The reaction mixture is thereafter stirred for 2 hours atambient temperature, filtered and the residue washed with ethyl acetate.The combined filtrates are extracted with ethyl acetate and the extractis dried and evaporated. The residue is taken up in diethyl ether,filtered and again evaporated. There is thus obtained 0.35 g. (28% oftheory) semi-crystalline 3-(5)-nitro-4-methylpyrazole.

1.4 g. of this compound is stirred under reflux for 4.5 hours with 1.8ml. methyl iodide and 1.6 g. potassium carbonate in 11.4 ml. ethyleneglycol dimethyl ether. The reaction mixture is then cooled, filtered andthe filtrate evaporated in a vacuum. The residue is taken up in ethylacetate, successively washed with aqueous potassium carbonate solution,aqueous sodium thiosulphate solution and finally with water, then driedand evaporated. There is then obtained 1.15 g. (74% of theory)semi-crystalline 1,4-dimethyl-3-nitropyrazole.

This is dissolved in 25 ml. of a mixture of equal parts by volume ofacetic acid and acetic anhydride. 1.9 ml. concentrated sulphuric acid isthen added dropwise and 2.2 g. chromium trioxide are added theretoportionwise. By means of occasional cooling, a temperature increaseabove 40° C. is avoided. After further stirring for 2 hours at 50° C.,the reaction mixture is poured on to ice, the pH value is adjusted to7.5-8 by means of a concentrated aqueous solution of ammonia and thereaction mixture is then extracted with ethyl acetate. After drying andevaporating the extract, there is obtained 0.8 g. (38% of theory) oily1-methyl-3-nitropyrazole-4-aldehyde diacetate, which is stirred with 8ml. 6N hydrochloric acid for 1 hour at 50° C. After cooling, thereaction mixture is extracted with ethyl acetate, dried and evaporated.There is thus obtained 0.45 g. (93% of theory)1-methyl-3-nitropyrazole-4-aldehyde, which is identical with the productdescribed in Example 1.

EXAMPLE 18. 3-(1-Methyl-3-nitro-4-pyrazolyl)-acrylonitrile Variant A

3.38 g. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylamide are stirred in 8.5ml. phosphorus oxychloride for 2 hours at 125° C. The reaction mixtureis then evaporated in a vacuum, cooled and the residue neutralised withice-cold aqueous ammonia solution. There are obtained 2.85 g. crude3-(1-methyl-3-nitro-4-pyrazolyl)-acrylonitrile. After recrystallisationfrom methanol-dioxan, with the addition of active charcoal, there isobtained 1.45 g. (48% of theory) of pure compound; m.p. 146°-148° C.

Variant B

1 g. 1-methyl-3-nitropyrazole-4-aldehyde and 0.66 g. cyanoacetic acidare stirred for 1 hour at 70° C. in 2 ml. pyridine and 0.06 ml.piperidine. The reaction mixture is then cooled and the reaction mixtureis acidified, filtered off with suction, washed with water and dried.0.1 g. of the product obtained is heated for 2.5 hours in 1 ml. pyridineat a bath temperature of 120° C., decarboxylation thereby taking place.Thereafter, ice-cold, semi-concentrated hydrochloric acid is addedthereto, followed by extraction with ethyl acetate. Evaporation of theextract gives 0.03 g. of the desired3-(1-methyl-3-nitro-4-pyrazolyl)-acrylonitrile; m.p. 146°-148° C. Themixed melting point with the product obtained according to Variant Ashows no depression.

EXAMPLE 19 3-(1-Methyl-3-nitropyrazolyl)-acrylamide

0.1 g. of the 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylonitrile preparedaccording to Example 18, Variant B, is dissolved in 1 ml. concentratedsulphuric acid and stirred for 1 hour at ambient temperature. Afterleaving the reaction mixture to stand overnight, ice is added theretoand the precipitated crystalline product is filtered off with suction,washed with water and dried. There is obtained 0.08 g. (73% of theory)of the desired 3-(1-methyl-3-nitropyrazolyl)-acrylamide. The mixedmelting point with the product obtained according to Example 3 shows nodepression.

EXAMPLE 20 Sodium 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylate

197 mg. 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid (preparedaccording to Example 1) are neutralized with a dilute aqueous solutionof sodium hydroxide. The clear solution is evaporated to dryness and theresidue is triturated with isopropanol. After filtering off with suctionand washing with diethyl ether, there are obtained 170 mg. of thedesired sodium salt; m.p. 306° C. (with foaming).

The antimicrobial activity of the instantly disclosed compounds wasconfirmed by the testing of a number of representative or illustrativecompounds in certain tests. In one series of test, the absolutebacteriostatic minimum concentration for each test compound wasdetermined and expressed in micrograms per milliliter. Thus, Table Ibelow sets forth, for each test compound, the maximum extent to whichthe test compound in question can be diluted and still exhibitbacteriostatic activity. As a comparison substance, there was used thecommercial bacteriostat known as "Furadantin", which is identifiedchemically as N-(5-nitrofuryliden)-1-amino-hydantoin. It will be seenfrom the data presented in Table I that the instantly claimed compoundsare substantially more active as bacteriostats than the comparisoncompound, i.e., Furadantin, in that much lower concentrations of thetest compounds were capable of acting bacteriostatically, relative tothe higher dosages of Furadantin required to achieve this effect. Thedata for Furadantin are presented at the end of Table I infra.

The following were the test compounds of the invention:

Compound I = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylamide

Compound II = 3-(1-ethyl-3-nitro-4-pyrazolyl)-acrylamide

Compound III = 3-(1-methyl-3-nitro-4-pyrazolyl)-N-hydroxyacrylamide

Compound IV = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid ureide

Compound V = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N-(pyrrolidinomethyl)-amide

Compound VI = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N-methylamide

Compound VII = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N-cyclopropylamide

Compound VIII = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N-cyanomethylamide

Compound IX = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic acid-thioureide

Compound X = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N-piperidinomethylamide

Compound XI = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N',N'-dimethylureide

Compound XII = 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylicacid-N-(N'-methylcarbamoyl)-amide

Compound XIII = 3-(1,5-dimethyl-3-nitro-4-pyrazolyl)-acrylamide

Comparison Compound:

Furadantin = N-(5-nitrofuryliden)-1-amino-hydantoin.

                                      TABLE 1                                     __________________________________________________________________________    Bacteriostatic Effect in Vitro                                                         Absolute Bacteriostatic Minimum Concentration in μg/ml                     Bacteria Type ( ) Strain                                             Active   Escherichia                                                                          Escherichia                                                                          Proteus  Pseudomonas                                   Compound coli (108)                                                                           coli (106)                                                                           mirabilis (298)                                                                        aeruginosa (71)                               __________________________________________________________________________    Compound I                                                                             0.25   0.125  128       64                                           Compound II                                                                            1      0.5                                                           Compound III                                                                           4      4      256       64                                           Compound IV                                                                            1      0.5                                                           Compound V                                                                             1      0.25                                                          Compound VI                                                                            1      0.5                                                           Compound VII                                                                           4      2                                                             Compound VIII                                                                          2      2                                                             Compound IX                                                                            1      1                                                             Compound X                                                                             1      0.25                                                          Compound XI                                                                            4      2      256      128                                           Compound XII                                                                           4      1      256      128                                           Compound XIII                                                                          1      0.5    256      256                                           Furadantin                                                                             4      4      256      128                                           __________________________________________________________________________

In another series of tests, the bacteriostatic activity of certainillustrative compounds of this invention in urine was tested and thepercentage of administered test substance excreted in the urine was wasdetermined, after oral administration, in rats. Again, the comparisonsubstance "Furadantin" (nitrofurantoin) was used in side-by-sidecomparisons. The results obtained are set forth in Table II below, inwhich the column headed "Maximal Dilution" represents the maximum extentto which the urine sample could be diluted and still exhibitbacteriostatic activity against the test bacterium, which wasEscherichia Coli (106). The test compounds were administered at the rateof 40 mg and 20 mg of test compound per kg of the rat's body weight, andare on the basis of 75 ml of urine per 22 hours after oraladministration of the test compound. Each test value is based on theaverages of values obtained in tests in nine rats and in the instanceswhere two or more values are set forth, two or more determinations weremade. The corresponding value for the reference standard "Furadantin" isset forth at the bottom of Table II. It can be seen that the compoundsrepresentative of the instant invention were capable of being diluted toa substantially greater extent than Furadantin, and still exhibitbacteriostatic activity; also, most of the compounds of the inventionwere excreted in urine to a much greater extent than Furadantin.

                  TABLE II                                                        ______________________________________                                        Bacteriostatic                                                                Activity in Urine in Rats after Oral Administration                                                Maximal Dilution                                         Test Substance         40 mg/kg 20 mg/kg                                      ______________________________________                                        3-(1-methyl-3-nitro-4-pyrazolyl)-acryl-                                                                       1 : 1707                                      amide                           1 : 1120                                                                      1 : 2880                                                                      1 : 1216                                      3-(1-ethyl-3-nitro-4-pyrazolyl)-acryl-                                                                        1 : 427                                       amide                                                                         3-(1-methyl-3-nitro-4-pyrazolyl)-N-                                           hydroxy-acrylamide     1 : 960  1 : 768                                       3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-(β-hydroxyethyl)-amide                                                                   1 : 235  1 : 111                                                                       1 : 168                                       3-(1,5-dimethyl-3-nitro-4-pyrazolyl)-                                         acrylamide             1 : 296  1 : 208                                                                       1 : 146                                       3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-(6-methyl-2-pyridyl)-amide                                                                    1 : 43                                                                        1 : 39                                                 3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-(pyrrolidinomethyl)-amide                                                                              1 : 875                                       3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-methylamide              1 : 616                                       3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-allylamide               1 : 152                                       3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-cyclopropylamide         1 : 84                                        3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-piperidine        1 : 120                                                3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                                             1 : 359  1 : 260                                       acid-N-isopropylamide                                                         3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-cyanomethylamide         1 : 270                                       3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N-piperidinomethylamide                                                                         1 : 348                                                3-(1-methyl-3-nitro-4-pyrazolyl)-acrylic                                      acid-N',N'-dimethylureide                                                                            1 : 94                                                 Furadantin                      1 : 19                                                                        1 : 21                                        ______________________________________                                    

In another series of tests, the in vivo effectiveness of the inventivecompounds in mice was determined, according to the following procedure.

Female mice (inbreeding strain NMRI), weight 19-21 g, were infected byinjecting 0.5 ml of a diluted 18-hour bouillon culture of EscherichiaColi (108) intraperitoneally into the animals. The intensity of theinfection was adjusted so that without treatment at least 95% of theanimals died during the first 2 days. 40 animals were used for theseinfection controls.

Treatment

The treatment took place directly after the infection in the form of asingle subcutaneous dose. The volume of the single dosage amounted to0.5 ml (substance dissolved in distilled water or 5% tylose mucus). 10animals were used in each test at each dosage.

In each case, 10 control animals were not infected but only treated withthe two highest dosages of the test substances. These control testsserved as a basis for determining the losses of animals caused by thetest compound.

The animals were observed for four days, the number of the deceasedanimals being determined daily, and the survival rate after four daysdetermined.

The results are set forth in Table III below.

                                      TABLE III                                   __________________________________________________________________________    In Vivo Tests in Mice                                                                     % Surviving Animals                                               Test Compound                                                                             320 mg/kg                                                                           160 mg/kg                                                                           80 mg/kg                                                                           40 mg/kg                                                                           20 mg/kg                                    __________________________________________________________________________    Compound I                        100                                         Compound II                        50                                         Compound III                       50                                         Compound V                        100                                         Compound VIII                      10                                         Comparison Substance:                                                         Penicillin G                                                                              100   90    40   0                                                __________________________________________________________________________

The particular mode of administration and dosage of inventive compoundto be applied in treating a given bacterial infection or infirmity will,of course, be determined by the physician, taking into account all thecircumstances of a particular case. However, in general, tabletscontaining the test compound to be administered per os, will containabout 250 mg of active material and, for local administration, maycontain about 500 mg of active substance. The dosage to be applied maybe one tablet taken in the morning and in the evening with thecorresponding meal, for, e.g., 10 consecutive days, if the compound isapplied per os. For local administration, one ovule may be applied for10 to 20 days every evening. In men, the per os administration may haveto be increased to, e.g., 750 mg to 1 g, instead of the standard 250 mgper tablet dosage.

In will be understood that the specification and examples areillustrative but not limitative of the present invention and that otherembodiments within the spirit and scope of the invention will suggestthemselves to those skilled in the art.

What is claimed is:
 1. 3-Nitropyrazole compound of the formula: ##STR5## wherein R₁ is lower alkyl;R₂ is hydrogen or lower alkyl; R₃ is cyano, carboxyl, or lower alkoxycarbonyl; and pharmaceutically acceptable salts thereof.
 2. 3-Nitropyrazole compound as claimed in claim 1 wherein R₁ is alkyl of up to 5 carbon atoms.
 3. 3-Nitropyrazole compound as claimed in claim 1 wherein R₂ is hydrogen.
 4. 3-Nitropyrazole compound as claimed in claim 1 wherein R₂ is alkyl of up to 5 carbon atoms.
 5. 3-Nitropyrazole compound as claimed in claim 1 wherein R₃ is cyano.
 6. 3-Nitropyrazole compound as claimed in claim 1 wherein R₃ is carboxyl.
 7. 3-Nitropyrazole compound as claimed in claim 1 wherein R₃ is alkoxycarbonyl of up to 5 carbon atoms in the alkoxy moiety.
 8. Anti-microbial composition comprising a pharmaceutically acceptable carrier and in anti-microbially effective amount, a 3-nitropyrazole compound as claimed in claim
 1. 9. Method of combatting microbial infections which method comprises administering to the afflicted subject anti-microbially effective amounts of a 3-nitropyrazole compound as claimed in claim
 1. 10. Method as claimed in claim 9 wherein the compound is applied to combat microbial infections in the urinary tract.
 11. Method as claimed in claim 9 wherein the compound is applied at a dosage of 250 to 1000 mg. 